Change shutdown behavior such that now first bdev destruct() call
stops OCF cache instance.
Previusly, cache was stopped when single vbdev was referencing it.
This patch is related to persistent metadata support.
Without this change, every time a SPDK application is stopped,
only the last core is remembered in metadata,
because vbdevs detach by 1 by 1, each time updating the metadata.
Change-Id: I57db3f77db525177c024ee85e660a85aff2f8c31
Signed-off-by: Vitaliy Mysak <vitaliy.mysak@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/455413
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
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